1. Field of the Invention
The invention relates to a locking device for linear actuators, in particular for fluid-actuated adjusting devices, with a piston rod mounted in an axially displaceable manner relative to a receiving device. The invention is suitable in particular for hydraulic adjusting devices that are used for safety-critical applications.
2. Discussion of Background Information
From prior art, hydraulic lockings in the form of a flow check valve are known for hydraulic adjusting devices. In particular for safety-critical applications in aviation, flow check valves for locking the hydraulic adjusting device are disadvantageous, since there is the possibility of leakage at each seal situated in the system. A malfunction of the valve can have serious consequences. Furthermore, volume changes of the hydraulic fluid are brought about by the temperature variations present in flight operation, which volume changes in the case of the hydraulic locking could lead to the exit of hydraulic fluid due to positive pressure or the entry of ambient air due to negative pressure.
Furthermore, frictional lockings via various clamping principles are known. The disadvantage of these is the high Hertzian pressure necessary to provide the required holding power. Moreover, the constructive expenditure of the clamping connections is extremely high and results in a high structural weight. The disadvantage of clamping connections is their tendency to be irreversible, so that after a locking, a release of the clamping connections is impossible or only possible with great difficulty.
From DE 31 33 117 C2 a support strut for retractable aircraft landing gear, the length of which strut can be changed telescopically, is known in which when a landing gear is completely retracted, a locking takes place in the end position by means of form-fitting. Locking in a non-retracted position is not possible.